U.S. patent number 5,253,735 [Application Number 07/951,822] was granted by the patent office on 1993-10-19 for apparatus to sense and annunciate truck brake condition.
Invention is credited to John V. Boes, Reese G. Larson.
United States Patent |
5,253,735 |
Larson , et al. |
October 19, 1993 |
Apparatus to sense and annunciate truck brake condition
Abstract
Three adjacent disks carried by an "S" cam shaft of a truck
brake system sense motion of system components beyond predetermined
limits to indicate need for adjustment and parts replacement and
annunciate such information at a distance from the brake system. A
first outer disk journaled on the "S" cam shaft is interconnected
to the slack adjuster arm to rotate responsive to motion of the
slack adjuster arm. A second medial disk journaled on the "S" cam
shaft is supported by external structure to remain stationary
relative to that shaft. A third outer disk is irrotatably carried
by the "S" cam shaft to rotate with it. The second medial disk
carries two Hall effect switches to sense the rotary position of
magnets carried in the first and third adjacent outer disks to
determine motion of the slack adjuster arm and the "S" cam shaft
beyond predetermined limits to indicate need for brake adjustment
and brake shoe replacement. Sensed data is transmitted to an
annunciator at a distance from the braking system. Separate sensing
and annunciating systems are provided for each braking system of a
truck-tractor and associated trailers.
Inventors: |
Larson; Reese G. (Spokane,
WA), Boes; John V. (Spokane, WA) |
Family
ID: |
25492200 |
Appl.
No.: |
07/951,822 |
Filed: |
September 28, 1992 |
Current U.S.
Class: |
188/1.11L;
192/30W; 324/207.2; 324/207.26; 340/454; 340/549 |
Current CPC
Class: |
B60T
17/22 (20130101); F16D 66/025 (20130101); F16D
2125/30 (20130101) |
Current International
Class: |
B60T
17/22 (20060101); B60T 17/18 (20060101); F16D
66/02 (20060101); F16D 66/00 (20060101); F16D
65/14 (20060101); F16D 066/02 () |
Field of
Search: |
;188/1.11 ;192/3W
;340/454,549 ;324/207.2,207.26 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Halvosa; George E. A.
Attorney, Agent or Firm: Bergman; Keith S.
Claims
Having thusly described our invention, what we desire to protect by
Letters Patent, and what we claim is:
1. In a braking system having opposed brake shoe arms pivotally
movable into frictional engagement with the circumferential rim of
a brake drum by means of an "S" cam carried for rotation on an "S"
cam shaft having an end extending externally of the brake drum and
activated by a radially extending adjustment arm having a clevis
interconnecting driving linkage spacedly adjacent the "S" cam
shaft, apparatus to sense and annunciate brake condition at a
distance from the brake system, comprising in combination:
a cam shaft disk having an elongate sleeve-like sensor body with
first and second ends defining a channel for carriage upon the
splined end of the "S" cam shaft, said body defining a disk bearing
surface and having clamping weans at the first end to releasably
positionally maintain at least a first end portion of the body upon
an "S" cam shaft, said body carrying an annular cam shaft disk at
the second end, said cam shaft disk carrying a first switching
means radially spaced from its bore;
an annular sensor disk journaled on the sleeve-like body of the cam
shaft disk adjacent the cam shaft disk, said sensor disk carrying
second and third switching means, respectively, on each side, said
second switching means operatively communicating with the first
switching means carried by the cam shaft disk, said sensor disk
having adjustable mechanical linkage to maintain the sensor disk in
fixed rotary position relative to the sleeve-like body carrying
it;
an annular slack adjuster arm disk rotatably carried by the
sleeve-like body of the cam shaft measuring disk adjacent the
sensing disk and spacedly distant from the cam shaft disk, said
slack adjuster arm disk having, forth switching, means in the
surface adjacent the sensor disk to operatively communicate with
the third switching means on the adjacent surface of the sensor
disk, said slack adjuster arm disk having an adjustably
positionable adjustment arm extending radially to communicate with
an outer end portion of the slack adjuster arm to cause the slack
adjuster arm disk to rotate responsively to the motion of the slack
adjustment arm; and
an annunciating system having at least two annunciators at a spaced
distance from the brake system, a first annunciator communicating
with the third switching means to annunciate the proximity of the
fourth switching means carried by the slack adjuster arm disk with
the third switching means proximate thereto to indicate need for
brake slack adjustment and a second annunciator to annunciate
proximity of the first switching means carried by the cam shaft
disk to the second switching means to indicate parts wear.
2. The apparatus of claim 1 wherein the annunciating system
is carried in the cab of a serviced truck and communicates with
each of a plurality of brake systems associated with a serviced
truck by electrically conductive wires, and
the annunciating system annunciates need for brake adjustment and
brake repair by means of visual indicia.
3. The invention of claim 1 further characterized by:
the end portion of the sleeve-like body distal from the cam shaft
disk being carried on the end portion of the "S" cam shaft
outwardly on that shaft from the communication of that shaft with
an associated slack adjuster arm.
Description
BACKGROUND OF INVENTION
RELATED APPLICATIONS
There are no applications related hereto heretofore filed in this
or any foreign country by any of the instant inventors.
FIELD OF INVENTION
This invention relates generally to wheeled vehicle braking
systems, and more particularly to apparatus to sense the condition
of an "S" cam type truck braking system and annunciates sensed data
at a distance from that braking system.
DESCRIPTION OF PRIOR ART
The braking systems in transport trucks have parts that wear and
are expendable and by reason of this such braking systems require
continuous surveillance for proper maintenance. Unfortunately many
braking systems, and especially the portions that are expendable,
are concealed or difficult of inspection and some require at least
partial dismantling to learn of their condition. Inspection
procedures are inconvenient and time consuming and consequently
brake system maintenance is often neglected to create substantial
safety hazards.
By far the greatest number of transport vehicle accidents that are
caused by vehicular equipment are caused in some fashion by braking
systems. Responsively, various sensing systems have heretofore
become known to sense and sometimes annunciate brake condition, but
no such systems have effectively resolved all of the associated
problems. The instant invention provides a new, novel and improved
member of this class of device.
Most over-the-road truck transport units of the present day are of
a compound type with a truck-tractor propelling one or more
trailers with each unit having one or more wheel trucks carrying
opposed sets of wheels. It is generally required for proper truck
operation and by various regulatory pronouncements that each wheel
or set of wheels on one axle end must have its own independent
braking system so that any transport unit has at least four braking
systems and the number may range upwardly to twelve or more such
systems. Almost universally truck braking systems have standardized
drum-type brakes with two arcuate shoe arms pivotally carried at
first adjacent ends inside a brake drum for expansion against the
inner surface of the drum to cause frictional braking action. The
shoe arms are expanded by an "S" cam that is rotated between second
adjacent ends of the opposed arms to cause both shoe arms to move
radially outwardly in substantially similar fashion. Our invention
is associated with the shaft carrying the "S" cam to measure both
the rotary motion of that shaft and angular motion of the
associated slack adjuster arm to determine need for adjustment and
brake shoe wear.
Most modern pneumatic braking systems have a diaphragm type
canister that applies motive force to a slack adjuster arm that in
turn rotates the "S" cam shaft for braking. A valve operated by the
brake pedal releases compressed air to the canister to move the
diaphragm. By the nature of this system, unlike hydraulic systems
common in automobiles, little if any indication of brake condition
is given to an operator. The pneumatic canister that applies
braking force is limited in its stroke and because of this
component wear, primarily of the brake shoes, can progress to the
point that the canister stroke is not enough to apply adequate
force to the brakes. Because of the high mechanical advantage built
into the system to provide larger motion of the air canister
diaphragm that is translated to a smaller motion of the brake
shoes, the wear condition is not well indicated to an operator by
brake function.
To promote safety through proper brake system maintenance,
regulatory agencies have established limits for travel allowable
for canister rods beyond which adjustments are required.
Unfortunately, component variations, lack of standard measuring
equipment and methods, and lack or proper enforcement often leave
doubt as to whether brake systems are in compliance.
Various devices have heretofore become known to sense motion
parameters of braking systems to determine system condition. The
most common parameter measured has been the movement of a cylinder
or diaphragm which ultimately moves the brake shoe arms. Other
devices have sensed the thickness of brake shoe lining, commonly by
sensing the distance between a brake shoe arm and the associated
brake drum, but also in some instances by sensing exposure of the
inner surface of a brake shoe lining. At least one prior device has
sensed the angular motion of the slack adjuster arm that rotates
the "S" cam shaft to indicate brake shoe lining wear. Some of these
sensing devices have annunciated the sensed condition at a distance
from the brake structure, but none have provided distant
annunciation combined with sensing the angular position of an "S"
cam shaft.
Most known brake condition sensors have been concerned with the
state of brake shoe linings, though the amount of "throw" or motion
required to actuate the braking system is generally of
substantially equal importance. "S" cam activated braking systems
generally may be adjusted by a slack adjustment mechanism which
changes the angular position of the "S" cam shaft at which rotary
motion is first applied to move that shaft. This allows a brake
system to be adjusted to accommodate wear of both the brake shoe
lining and of the "S" cam and its contacting pins, thereby staying
within the limits of motion of the linkage. If slack adjustment is
not properly made, the air canister rod stroke may not be
sufficient to properly operate the braking system and if shoe wear
is great the "S" cam can even rotate off brake shoe contact pins to
cause a braking system to become inoperative.
The need for slack adjustment in the past has generally been
determined by loss or delay of braking action, by disassembly and
inspection of the braking system, or by measurement of canister rod
extension. Our sensing system in contradistinction provides sensing
apparatus to dynamically determine slack in the brake system
exceeding a predetermined amount and to annunciate this condition
at a distance from the braking system. The system also accommodates
changes in the amount of slack and the angular position at which
braking is initiated to allow and account for adjustments in a
brake system.
Known devices that sense and annunciate brake condition generally
have annunciated the results of their sensations only in the
immediate vicinity of the brake system itself. This limits the
utility of such devices as brake systems are located in positions
that are difficult of access and accessible only when a truck is
not moving. Our system provides remote annunciation at any time at
positions distant from the brake system being sensed. This is
accomplished either by direct wire communication or by an aerial
type communication such as radio. The system provides annunciators
for each of a plurality of individual braking systems in a
truck-trailer unit and may be conveniently located in the cab of a
truck. An annunciating system may also be used spacedly distant
from a truck such as by regulators, law enforcement agent, and the
like when checking braking systems of a truck for regulatory
compliance.
Our invention lies not in anyone of these features per se, but
rather in the synergistic combination of all of the structures of
our device that necessarily give rise to the functions flowing
therefrom as herein set forth and claimed.
SUMMARY OF INVENTION
Our invention provides a system to sense excessive wear of parts
and excessive slack in "S" cam type braking systems and annunciate
the sensed conditioned at a distance from the brake system.
We provide three adjacent relatively pivotal disks that are carried
by the "S" cam shaft. The first outer disk is journaled on the "S"
cam shaft and interconnected with the slack adjuster arm to rotate
responsive to rotary motion of the slack adjuster arm. The second
sequentially adjacent medial disk is journaled on the "S" cam shaft
and supported by brake structure to remain stationary relative to
the vehicle "S" cam shaft. The third sequentially adjacent outer
disk is irrotatably carried by the "S" cam shaft. The first and
third disks carry magnets that each operatively communicate with
one of two Hall effect switches carried by the second medial disk
to activate those switches when the angular motion of the first or
third disks moves the magnets carried thereby into adjacency with
the associated Hall switches to indicate excessive slack and
excessive brake shoe wear respectively. The Hall effect switches
communicate electrically with an annunciator at a spaced distance
from the brake system to annunciate the existence or non-existence
of switch operation. A plurality of annunciators may be associated
to indicate at a single location the condition of all brake system
sensors on a truck and trailer unit.
In providing such apparatus it is:
A principal object to sense the rotation of the "S" cam shaft and
slack adjuster arm of a truck brake system relative to adustable
predetermined limits to indicate need for brake shoe lining
replacement and slack adjustment.
A further object is to provide annunciations of the sensed
conditions at a distance from the brake system, commonly either in
the cab of a service truck or spacedly adjacent to the truck.
A further object is to provide annunciation at a single location of
the conditions of a plurality of brake systems in a truck and
trailer unit.
A still further object is to provide such apparatus that may be
attached to most "S" cam type braking systems in presently existing
trucks and trailers.
A still further object is to provide such apparatus that is of new
and novel design, of rugged and durable nature, of simple and
economic manufacture and otherwise well adapted to the uses and
purposes for which it is intended.
Other and further objects of our invention will appear from the
following specification and accompanying drawings which form a part
hereof. In carrying out the objects of our invention, however, it
is to be remembered that its accidental features are susceptible of
change in design and structural arrangement, with only one
preferred and practical embodiment of the best known mode of our
invention being specified and illustrated in the accompanying
drawings as is required.
BRIEF DESCRIPTION OF DRAWINGS
In the accompanying drawings which form a part hereof and wherein
like numbers of reference refer to similar parts throughout:
FIG. 1 is an orthographic, outwardly looking elevational view of a
typical brake drum with brake shoes and activating "S" cam
structure in position therein, but with the slack adjuster
mechanism removed, to show the general type of braking system with
which our invention is operable.
FIG. 2 is an orthographic end view of the interconnection of an "S"
cam shaft with a slack adjuster arm showing the adjustment linkage
in dashed outline.
FIG. 3 is a partially cut-away orthographic side view of the
interconnecting structure of FIG. 2 showing the same structure from
this aspect.
FIG. 4 is a view similar to that of FIG. 1, but with the slack
adjuster mechanism and our sensor apparatus in place on the
system.
FIG. 5 is an orthographic side or elevational view of a part of the
"S" cam shaft and slack adjuster structure shown in FIG. 3 with our
apparatus in place thereon.
FIG. 6 is a partial cut-away orthographic elevational view of the
left side of the structure illustrated in FIG. 5.
FIG. 7 is a somewhat enlarged, partial horizontal cross-sectional
view through the structure of FIG. 5, taken on the line 7--7
thereto in the direction indicated by the arrows thereon, with the
associated "S" cam structure included.
FIG. 8 is an enlarged portion of FIG. 7 shown within the dashed
ellipse 8 on FIG. 7.
FIG. 9 is a diagrammatic representation of the face of an
annunciator for use with our device and associated electrical
circuitry shown in normal symbology.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Our invention generally provides sensing apparatus 11 associated
with truck brake system 10 to sense the system condition and
transmit sensed information to annunciator 12 at a spaced distance
from the brake system.
A typical "S" cam type truck braking system is shown in FIGS. 1, 2
and 3 where it is seen to include brake drum disk 13, with
perpendicularly extending peripheral cylindrical rim 15, attached
to axle housing 14 and axle shaft 12. Two similar paired,
symmetrically opposed brake shoe arms 16 carrying radially
outwardly extending arcuate brake shoes 17 are carried on pins 18
within rim 15 for pivotal motion toward and away from the rim. The
adjacent movable ends 16a of the brake shoe arms carry
perpendicularly extending "S" cam pins 19 so positioned that the
pins 19 will be spacedly adjacent to allow operative positioning of
"S" cam 22 therebetween. The "S" cam shaft 20 is carried in support
bearing 24 which in turn is supported on axle housing 14 by bracket
21 to extend a spaced distance (within the brake drum disk). "S"
cam shaft 20 irrotatably carries "S" cam 22, commonly formed as a
unitary structure with the "S" cam shaft. The "S" cam is of the
particular shape for which it was named, as illustrated in FIG. 1,
so that as the cam rotates in a clockwise direction in the instance
illustrated in FIG. 1, it will simultaneously move adjacent "S" cam
pins 19 radially outwardly to move brake shoes 17 into frictional
contact with the inner surface of drum rim 15 to cause frictional
braking action. The two brake shoes are maintained in a biased
non-braking position by extension spring 23 communicating between
the two end portions 16a.
The end portion 20b of the "S" cam shaft extending from the brake
drum is supported in bearing 24 carried by the frame of a vehicle
and defines end spline 25 in its outermost portion. The splined end
portion of the "S" cam shaft irrotatably carries slack adjuster arm
26 extending radially therefrom and axially maintained thereon by
keeper ring 79. The slack adjuster arm rotatably carries annular
adjustment collar 27, which on its radially inner surface interfits
with spline 25 to provide an irrotatable interconnection and on its
radially outer surface defines worm gear 28 about its periphery.
Adjustment collar 27 is rotatably carried by the slack adjustment
arm to cooperatively contact spiral worm 29 to regulate the angular
positioning of the adjustment collar relative to the slack
adjustment arm. The spiral worm 29 provides adjustment shaft 30
having a nut-like end extending from the slack adjuster arm to
allow adjustment of rotary positioning of these elements to adjust
the brake system for slack caused by wear of parts, especially the
brake lining, the "S" cam and the "S" cam pins, by moving the
angular position at which force is first applied to the "S" cam
shaft. Spring loaded locking collar 30a keeps adjusting screw 30
and spiral worm 29 from accidentally turning once setting is
correct.
In this braking system, rotary motion is provided to the "S" cam
shaft by angular motion of the slack adjuster arm 26 responsive to
substantially linear force applied to the radial outer end thereof
through clevis 31 and clevis pin 32 by a pneumatic or hydraulic
canister 77 which ultimately is operated by a brake pedal in the
cab of a truck. Commonly the fluid operating system is of a
fail-safe type which causes motion of clevis 31 responsive to
lowered pressure in the fluid operating system, so that if the
pressure system fails, the brake system assumes a braking mode.
Such braking systems, in the essence described at least, are common
in most present day transport trucks and trailers of commerce and
have become reasonably standardized substantially in the form as
illustrated and described. Similar systems may be used with other
wheeled land vehicles, and especially those running on rails. It is
with such brake systems that our invention is operative.
Our invention is illustrated especially in FIGS. 4 et seq., of the
drawings. Sensing apparatus 11 provides a structure carried on the
outer splined end portion 20b of "S" cam shaft 20 and extends
radially therefrom.
Sensing apparatus 11 provides sleeve-like cylindrical body 33
defining medial channel 34 to fit over and fasten upon the outer
splined end portion 20b of "S" cam shaft 20. The body 33 extends a
spaced distance from the "S" cam shaft and defines in its outer end
portion annular, radially outwardly extending cam shaft measuring
disk 35. Body 33 is releasably maintained in irrotatable engagement
on the outer end portion of the "S" cam shaft by split ring clamp
36 that extends about the inner end portion of the body. The split
ring clamp defines a bore having an inner diameter substantially
the same as the outer diameter of the adjacent portion of the body
33. The clamp 36 is defined by two similar semi-circular portions
interconnected by threadedly engaged bolts 37 which may be
tightened to frictionally engage body 33 upon the end portion of
"S" cam shaft. Body 33 defines plural spaced slots 42 extending
spacedly from its inner end to create resilience to allow clamping
onto end portion 20b of the "S" cam shaft. Clamp 36 provides a
radially inwardly extending keeper ring 58 that engages keeper ring
groove 78 to provide secure attachment to splined end 20b of the
"S" cam shaft.
The radially outer portion of body 33 axially inward of measuring
disk 35 defines disk bearing surface 38 to journal annular sensing
disks. The inner "S" cam facing surface of measuring disk 35
defines an appropriate annular groove to carry "O" ring 39 of
circular cross-section which serves as a dirt and moisture barrier.
A small permanent magnet 40 is carried in an appropriately defined
hole in the same inner surface of disk 35, radially inwardly from
"O" ring 39, to allow sensation of the radial position of that disk
as hereinafter specified.
Annular sensor disk 41 is journaled on bearing surface 38
immediately inwardly toward the "S" cam shaft from cam shaft
measuring disk 35. Sensor disk 41 is of greater external diameter
than cam shaft measuring disk 35 to allow fastening of yoke 47. The
radially inner portion of sensor disk 41 carries two Hall effect
switches 43, 114 in appropriate holes defined in each side of the
disk at a radial position similar to that of magnet 40 carried by
disk 35 so that the Hall effect switch and magnet that are adjacent
each other may rotate into coincidence. Channel 45 is defined in
the sensor disk 41 to extend from each of the Hall effect switches
outward through the circumferential periphery of the disk to
provide a channel for electrical circuitry 46 extending between
annunciator 12 and the Hall effect switches 43, 44.
The annular sensor disk 41 is positionally maintained relative to
"S" cam shaft by yoke 47 carried by the outer rim portion of disk
41 by means of bolts 48 threadedly engaged between these elements.
Yoke 47 defines slot 49 to receive rod 50 which carries adjacent
nuts 51 engaged on the threaded opposite end portion to fasten that
end portion of the rod in support arm 52 supported on bearing 24 by
bolts 53 extending in threaded engagement between these elements.
This arrangement of elements provides an adjustable support system
that may be attached to existing brake systems with the rest of
sensing apparatus 11 to maintain annular sensor disk 41 in a fixed
position relative to the "S" cam shaft of that brake system.
Slack adjuster arm disk 54 defines bore 55 for journaling upon disk
bearing surface 38 of body 33. The main body of disk 54 is of
substantially the same radial size as that of cam shaft measuring
disk 35. On its inner side proximate to the "S" cam, adjustment arm
disk 54 defines radially extending adjustment annulus 56 defining
annular adjustment groove 57 in its outwardly facing surface. The
planar surface of slack adjuster arm disk 54 that is adjacent to
sensor disk 41 defines an appropriate groove to carry annular "O"
ring 58a and the surface defining bore 55 defines a similar annular
groove to carry "O" ring 59 to serve as dirt and moisture
barriers.
Slack adjuster connector arm 60 extends radially outwardly from
releasably adjustable interconnection with slack adjuster arm disk
54 to communicate with the linkage driving the slack adjuster arm
26 to translate the arcuate motion of that arm into responsive
motion of the slack adjuster arm disk 54. The slack adjuster
connector arm 60 is releasably interconnected to adjustment annulus
56 by asymmetrical "U" shaped clamp 61 having bolts 62 extending
therethrough and into threaded engagement with the connector arm
60, as illustrated especially in FIGS. 5 and 6. The adjustment arm
extends across the inner "S" cam facing surface of adjustment
annulus 56 and the radially inner arm of fastening clamp 61 extends
into adjustment groove 57 so that the elements may be releasably
fastened upon the adjustment annulus by bolts 62. The medial
portion of slack adjuster connector arm 60 defines offset 63 to
allow appropriate positioning of its two end portions and the
radially outer end portion of the adjustment arm defines slot 64 to
receive the body of the clevis pin 32 in a movable and adjustably
interconnection. With this interconnecting structure, slack
adjuster connector arm 60 may be adjustably interconnected to slack
adjuster arm disk 54 at various radial positions, and when so
interconnected will translate arcuate motion of clevis pin 32 into
responsive rotary motion of slack adjuster arm disk 54.
Immediately inwardly of the slack adjuster arm disk 54 and proximal
to the "S" cam, bearing surface 38 carries wave spring 65 and
keeper ring 66 engaged in groove 67 defined in the radially outer
peripheral surface of body 33 to maintain the annular sensor disk
41 and slack adjuster arm disk 54 in appropriate axial alignment on
bearing surface 38 and yet allow the rotation of those two disks
relative to each other and relative to the body 33.
The outer planar surface of slack adjuster arm disk 54 carries
small permanent magnet 68 in a hole defined in its surface adjacent
sensor disk 41. This magnet is radially positioned to rotate into
coincidence with switch 44 carried by the sensor disk.
Annunciator 12 is illustrated in diagrammatic form and normal
symbology in FIG. 9. Switches 43, 44 communicate in parallel with
power source 69 through line 70. Switch 43 then communicates
through line 71 to annunciator 72, which in the instance
illustrated is a light, to common battery return line 74. Switch 44
communicates in similar fashion through line 75 and annunciator 76
to brake system switch 73 and thence through line 74 to battery 69.
With this annunciating system, a particular braking system may be
selected by use of switch 73 and the condition of that system then
displayed by means of annunciators 72, 76, or if desired switch 73
may be omitted to maintain the system on at all times. A plurality
of such braking systems may have similar annunciating systems
carried at one location for sequential or simultaneous display at
that point, commonly in the cab of a truck or at a position
spacedly distant from a truck.
The annunciating circuitry per se is not new or novel and various
known sophisticated designs and elements may be added to the system
to increase the utility of its use. Various types of audible or
visual annunciators may be used in the system as desired.
Electronic circuitry, and especially low voltage systems using
diodes and thyristors, may be used to lock on any of the
annunciators once activated until either manually reset or the
happening of some other contingency. It is possible that the
wire-type communication of components illustrated might be replaced
with wireless type communications, such as radio signals or the
like. These various annunciating concepts are known in their
essence at least and their details do not constitute a part of our
invention per se, though they are included within its scope.
Having thusly described the structure of our invention, its use may
be understood.
Sensing and annunciating apparatus is created as specified and
installed on an "S" cam type braking system as described. It is to
be particularly noted that our system accommodates design and
configurational variations and adjustments to permit the system to
be installed on brake systems having somewhat variable parameters.
"S" cam braking systems of the present day trucking arts are
reasonably standardized and the adjustment limits allowed by our
invention permit use on substantially all existing braking systems,
and if not, our system may generally be readily reconfigured by
known engineering methods to allow such use.
For installation, adjuster arm keeper ring 79 is removed and split
ring clamp 36 is relaxed sufficiently to allow placement of the
sensor body 33 upon the "S" cam shaft 20. Sensor body 33 is placed
over the end portion 20b of the shaft 20, the split ring clamp 36
is moved over the inner end of the body and bolts 37 of the clamp
are tightened to releasably fasten the body 33 on the "S" cam
shaft. Holes are established in the peripheral flange of the
housing of bearing 24 for bolts 53 and are threaded to accept those
bolts. Fastening arm 52 is attached to bearing 24 by establishing
bolts 53 between the two elements so that rod 50 is carried within
channel 49 of yoke 47.
Slack adjuster connector arm 60 is positioned on adjustment annulus
56 by positionally establishing it and subsequently fastening it by
bolt 62. Clevis pin 32 is removed from clevis 31, the outer end of
adjustment arm 60 is manually positioned so that the clevis pin may
be reinserted through slot 64, and the clevis pin is reinserted
through that slot and through its normal channels in clevis 31
where it is again releasably fastened. In this condition, the
sensing apparatus is operatively established on a particular brake
system.
After sensing apparatus placement, electrical wiring of the
annunciator system is established to allow placement of the
annunciator as desired. Commonly all of a group of annunciators, or
a single annunciator switched to sequentially display all sensor
systems in a single vehicle, will be positioned at the same
location, usually in a single unified display panel or box in a
truck cab.
In operation, the rotary motion of the cam shaft past a
predetermined initial point is measured by cam shaft measuring disk
35 and the amount of rotary motion of the cam shaft is measured by
motion of slack adjuster arm disk 54, both disk motions being
determined relative to annular sensor disk 41. In the braking
system illustrated in FIG. 4, et seq., brake shoes 17 will be moved
toward the inner surface of brake drum rim 15 when clevis 31, moves
to the left in that illustration thus causing clockwise rotary
motion in the "S" cam shaft. When our system is installed the
angular relationship of cam shaft measuring disk 35 and slack
adjuster arm disk 54 are determined relative to sensor disk 41. The
two Hall switches 43, 44 carried by the sensor disk 45 are normally
positioned in a vertically upward position, and this position is
maintained throughout the installation process.
The magnet 40 carried by the cam shaft measuring disk 35 is
established an angular distance clockwise from switch 43, the
distance being that which is predetermined by ordinary engineering
methods to indicate a wear of the braking system such as to require
replacement of its parts. The components causing this wear will be
predominantly the brake shoe elements and secondarily the surface
of "S" cam 22 or "S" cam pins 19, or a combination of wear of all
of these elements. The slack adjuster arm disk 54 will have its
magnet 68 positioned at an angular distance clockwise from the
inner Hall switch 44 as determined by the amount of slack or throw
of clevis 31 that may be allowable within the limits of safety,
again as determined by known and established engineering
methods.
The setting of these parameters may be readily accomplished by
firstly rotating the "S" cam to its neutral or "lowest roller"
position, positioning the sensor device on an "S" cam shaft,
fastening yoke 47 in appropriate angular position, and thereafter
rotating cam shaft measuring disk 35 to its appropriate radial
position before fastening split ring clamp 36. The slack adjuster
arm disk 54 is then rotated to its appropriate radial position
before fastening "U" shaped fastening clamp 61 upon that disk 54.
Installation is aided by the magnetic switch 44 positioned at the
switch "firing point" and then rotating the slack adjuster arm disk
54 in the appropriate angular amount before clamping slack adjuster
connector arm 60 in operating position.
As the brake system operates and the rotation of the "S" cam shaft
is sufficient to cause switch 44 to sense the presence of magnet 68
carried by the slack adjuster arm disk 57, that switch 44 will
close and allow current to pass from power source 69 through line
70 and switch 44 and thence through annunciator 72 to activate that
annunciator to indicate a dangerous wear condition and need to
adjust the brake system. As repeated adjustments are made and the
amount of angular motion of the "S" cam shaft 20 is great enough,
magnet 40 carried by cam shaft measuring disk 35 will rotate into
proximity with switch 43 to again close the electrical circuit
through that switch and cause annunciator 76 to activate to
indicate a need for replacement of brake shoes.
Normally brake system slack is adjusted by moving the angular
position of slack adjuster arm 26 relative to "S" cam shaft 20 by
releasing locking collar 30a, turning nut 30 to operate spiral worm
29 and rotating adjustment collar 27 relative to the slack adjuster
arm.
The foregoing description of our invention is necessarily of a
detailed nature so that a specific embodiment of its best mode of
operation might be set forth as required, but it is to be
understood that various modifications of detail, rearrangement and
multiplication of parts might be resorted to without departing from
its spirit essence or scope.
* * * * *